An anaerobic spriochete, Treponema hyodysenteriae, has been characterized as the primary etiological agent in swine dysentery. Harris, D. L.; Glock, R. D.; Christensen, C. R.; and Kinyon, J. M.: Vet. Med./Small Animal Clin. 67:61 (1972); Taylor, D. J.; and Alexander, T. J. L.: Brit. Vet. J. 127:108 (1971). But relatively little is known about the immunology of swine dysentery although resistance to reinfection can be demonstrated in convalescent pigs. In 1976, Glock et al reported that parenteral vaccination of pigs with killed cells of a virulent isolate of T. hyodysenteriae provided a significant degree of protection against subsequent intragastric challenge with live virulent T. hyodysenteriae. Glock, R. D., Schwartz, K. J., and Harris, D. L., Proceedings, International Pig Veterinary Society Congress, June 1976, Ames, Iowa. The vaccine was given in six intravenous injections at 6-day intervals. This was the first reported success in immunizing swine against swine dysentery infection.
Hudson et al found that oral dosing of an attenuated strain of T. hyodysenteriae provided no protection against subsequent challenge. Hudson, M. J., Alexander, T. J. L., Lysons, R. J., Wellstead, P. D., Brit. Vet. J. (1974) 130:37. Subsequently, Hudson et al attempted to immunize pigs with live attenuated T. hyodysenteriae using a combination of oral dosing and parenteral inoculation. Hudson, M. J., Alexander, T. J. L., Lysons, R. J., Prescott, J. F., Res. Vet. Science (1976) 21:366. Oral doses were administered on three consecutive days, and after an interval of several days, intraperitoneal vaccinations were administered, which were followed after several more days with intramuscular vaccinations. The overall results of these tests were summarized as follows: "Although vaccination appeared to enhance immunity to swine dysentery, half of the vaccinated pigs developed the disease. This level of protection would be unlikely to be of practical value in the field."